DESCRIPTION

The slk* functions manipulate the set of soft function-key labels that exist on
many terminals.
For those terminals that do not have soft labels,
curses takes over the bottom line of stdscr, reducing the size of
stdscr and the variable LINES.
curses standardizes on eight
labels of up to eight characters each.
In addition to this, the ncurses
implementation supports a mode where it simulates 12 labels of up to five
characters each.
This is useful for today's PC-like enduser devices.
ncurses simulates this mode by taking over up to two lines at
the bottom of the screen;
it does not try to use any hardware support for this
mode.

The slk_init routine must be called before initscr or newterm
is called.
If initscr eventually uses a line from stdscr to
emulate the soft labels,
then fmt determines how the labels are arranged on the screen:

0

indicates a 3-2-3 arrangement of
the labels.

1

indicates a 4-4 arrangement

2

indicates the PC-like 4-4-4 mode.

3

is again the PC-like 4-4-4 mode,
but in addition an index line is generated, helping the user to
identify the key numbers easily.

The slk_set routine
(and the slk_wset routine for the wide-character library)
has three parameters:

labnum

is the label number, from 1 to 8
(12 for fmt in slk_init is 2 or 3);

label

is be the string to put on the label,
up to eight
(five for fmt in slk_init is 2 or 3)
characters in length.
A null string or a null pointer sets up a blank label.

fmt

is either
0, 1, or 2, indicating whether the label is to be
left-justified, centered, or right-justified, respectively, within the
label.

The slk_refresh and slk_noutrefresh routines correspond to
the wrefresh and wnoutrefresh routines.

The slk_label routine returns the current label for label number
labnum, with leading and trailing blanks stripped.

The slk_clear routine clears the soft labels from the screen.

The slk_restore routine restores the soft labels to the screen
after a slk_clear has been performed.

The slk_touch routine forces all the soft labels to be output
the next time a slk_noutrefresh is performed.

The slk_attron, slk_attrset, slk_attroff and slk_attr
routines correspond to attron, attrset, attroff and attr_get.
They have an effect only if soft labels are simulated on the bottom line of
the screen.
The default highlight for soft keys is A_STANDOUT (as in
System V curses, which does not document this fact).

The slk_color routine corresponds to color_set.
It has an effect only
if soft labels are simulated on the bottom line of the screen.

RETURN VALUE

These routines return ERR upon failure and OK (SVr4 specifies only "an
integer value other than ERR") upon successful completion.

X/Open defines no error conditions.
In this implementation

slk_attr

returns the attribute used for the soft keys.

slk_attroff, slk_attron, slk_clear, slk_noutrefresh, slk_refresh, slk_touch
return an error
if the terminal or the softkeys were not initialized.

slk_attrset

returns an error
if the terminal or the softkeys were not initialized.

slk_attr_set

returns an error
if the terminal or the softkeys were not initialized, or
the color pair is outside the range 0..COLOR_PAIRS-1,
or opts is not null.

slk_color

returns an error
if the terminal or the softkeys were not initialized, or
the color pair is outside the range 0..COLOR_PAIRS-1.

slk_init

returns an error
if the format parameter is outside the range 0..3.

slk_label

returns NULL on error.

slk_set

returns an error
if the terminal or the softkeys were not initialized, or
the labnum parameter is outside the range of label counts, or
if the format parameter is outside the range 0..2, or if
memory for the labels cannot be allocated.

NOTES

Most applications would use slk_noutrefresh because a
wrefresh is likely to follow soon.

PORTABILITY

The XSI Curses standard, Issue 4, describes these functions.
It changes the
argument type of the attribute-manipulation functions slk_attron,
slk_attroff, slk_attrset to be attr_t, and adds const
qualifiers.
The format codes 2 and 3 for slk_init() and the
function slk_attr are specific to ncurses.